This invention relates generally to rotating or spinning blades, such as may be found in robots used in conjunction with semiconductor fabrication equipment, and more particularly to detecting vibration of such blades.
Robots are increasingly being used in many different applications, including semiconductor device fabrication. A robot can be generally and non-restrictively defined as a stand-alone hybrid computer system that performs physical and computational tasks. It is a multiple-motion device with one or more arms and that is capable of performing many different tasks. It can be designed similar to human form, although most industrial robots do not resemble people at all. Robots are used extensively in manufacturing, including semiconductor device fabrication.
FIG. 1 shows a robot 100 that is used in conjunction with semiconductor device fabrication. The robot 100 includes a process chamber 102, the sidewalls of which meet at a base at the bottom to form a cavity 104. A blade assembly 108 is positioned at the bottom of the base of the chamber 102, and rotates around an axis of rotation 106 at the center of the base of the chamber 102. The blade assembly 108 has a primary wafer blade 110, an auxiliary wafer blade 112, a straight wing 114, and an angled wing 116. The wafer blades 110 and 112 each have a base portion and a tip portion, the latter which is extensible from the center of the base of the chamber 102 to the sidewall of the chamber 102. The blade assembly 108 is used to transfer semiconductor wafers among different wafer orientation chambers, such as may include the chambers 118a, 118b, 118c, and 118d. The robot 100 may be a Centura robot as is available from Applied Materials, Inc., of Santa Clara, Calif.
A potential problem with the robot 100 is when the primary blade 110 begins to vibrate, moving up and down besides just rotating. This is shown in FIG. 2. From the center 106, the blade 110 should be located as is indicated in FIG. 2. However, when it vibrates, it moves up and down, from and to the positions 202 and 204. The vibration of the wafer blade 110 can have disadvantageous consequences. A semiconductor wafer may slide out, or may be damaged by the vibrating blade 110, since it is typically located only 1.5 millimeters from the blade 110. Furthermore, vibration may indicate that the robot 100 is becoming damaged, such as the bearings thereof that control the movement of the primary blade 110.
Therefore, there is a need for detecting blade vibration. Such blade vibration detection should ensure that semiconductor wafers are not damaged. Such blade vibration detection should also provide an early warning that the robot of which the blade is a part is becoming damaged. For these and other reasons, there is a need for the present invention.
The invention relates to detecting blade vibration via ultrasonic waves. The blade may be part of a robot that is used in conjunction with semiconductor device fabrication. A process chamber is provided that has a sidewall and a base defining a cavity contained therein. A rotatable blade is mounted at a center of the cavity that has a base portion and a tip portion extensible from the center to the sidewall of the process chamber. One or more ultrasonic sensors are mounted on the base adjacent to the sidewall. Ultrasonic waves are sent and received toward and reflected by the tip portion of the wafer blade to determine the tip portion""s position. In this way, vibrational movement of the blade can be detected.
Embodiments of the invention provide for advantages over the prior art. If vibration exceeds specifications, then the blade can be stopped, or an operator can be notified that the blade should be stopped. This prevents damage to semiconductor wafers, as well as to the blade or the robot itself. Furthermore, detection of vibration provides an early warning that the robot may be becoming damaged, and thus should be investigated. Still other aspects, embodiments, and advantages of the invention will become apparent by reading the detailed description that follows, and by referring to the accompanying figures.